JP2007196392A - Injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the injection device of a molding machine which can remove an adverse effect on a molding by water contained in a resin by maintaining the resin immediately before being melted in a dry state. <P>SOLUTION: The injection device has a cylinder 11 to which a molding material is supplied and a metering member 13 which is driven in the cylinder 11 to weigh the molding material. The cylinder 11 has a material supply hole 11b to which the molding material is supplied. Dry gas heated at a prescribed temperature is supplied to the vicinity of the material supply hole 11b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an injection molding machine, and more particularly to an injection apparatus that melts and injects a screw while heating resin in a cylinder.

  Generally, granular or pellet-shaped resin is supplied from a hopper to a heating cylinder of an injection molding machine. The raw material resin supplied to the heating cylinder is heated by the heating cylinder and melted by applying a shearing force by a screw that reciprocates while rotating in the heating cylinder. The molten resin is injected into the mold from the nozzle at the tip of the heating cylinder.

  If the molten resin contains moisture, the quality of the molded product will be adversely affected. Therefore, the resin supplied to the hopper is generally dried before being supplied to the hopper or in the hopper to remove the moisture. . Usually, the resin is dried by exposing the resin to hot air at a predetermined temperature.

As a technique for supplying a gas other than hot air to the resin, a technique for supplying an inert gas to the resin supplied to the heating cylinder has been proposed (see, for example, Patent Document 1). The supply of the inert gas forcibly expels the gas generated from the molten resin so that bubbles are not included in the molten resin. It has also been proposed to supply an inert gas to the resin before melting to remove oxygen and prevent oxidation of the resin.
JP 2004-50415 A

  In the molding process of a resin molded product of a normal size, for example, the dried resin supplied to a hopper having a volume of 1 liter is continuously molded into a tens of minutes to several hours. All of them are melted and injected by the heating cylinder. However, for example, when one molded product is very small (in the case of molding with a small shot volume), even if it is continuously molded, only about 100 g of resin may be used per day. In such a case, the resin before melting stays in the hopper and in the vicinity of the supply port of the heating cylinder for a long time.

  When the resin before melting stays in the hopper and near the supply port of the heating cylinder for a long time, the resin may not absorb the moisture again during the stay and may not be kept dry. In particular, in inline type injection devices, the screw shaft extends from the rear side of the water-cooled cylinder, which is the part to which the hopper is connected. There is a risk of moisture entering the water-cooled cylinder.

  Thus, in the case of molding with a small shot volume, even if the resin after the drying treatment is supplied to the hopper, the moisture is again absorbed in the hopper or the water-cooled cylinder until the resin is melted. There is a problem. Depending on the type of resin, this moisture may adversely affect the molded product. For example, when the moisture contained in the resin is injected together with the molten resin from the gate portion, radial streaks called silver stripes may appear on the surface of the molded product. Such a silver strip not only impairs the appearance of a molded product, but if the molded product is an optical component such as a lens, the function as an optical component is impaired.

  The present invention has been made in view of the above-described problems. By maintaining the resin immediately before being melted in a dry state, an injection of a molding machine capable of removing the adverse effect on the molded product due to moisture contained in the resin. An object is to provide an apparatus.

  In order to achieve the above-described object, according to one aspect of the present invention, there is provided an injection apparatus including a cylinder to which a molding material is supplied and a measuring member that is driven in the cylinder and measures the molding material. The cylinder has a material supply hole through which the molding material is supplied, and has a means for supplying dry gas heated to a predetermined temperature to the vicinity of the material supply hole in the cylinder. A featured injection device is provided.

  According to another aspect of the present invention, there is provided an injection apparatus including a cylinder to which a molding material is supplied, and a measuring member that is driven in the cylinder and measures the molding material. Injection having a material supply hole through which material is supplied, and means for supplying dry gas generated by compressing and dehumidifying gas to the vicinity of the material supply hole in the cylinder An apparatus is provided.

  In the above-described injection device, the dry gas is preferably a gas having the same composition as the ambient atmosphere. Alternatively, the dry gas may be an inert gas. It is preferable that the humidity of the dry gas is lower than the humidity of the atmosphere in the cylinder.

  In the above-described injection device, it is preferable that the cylinder has a dry gas supply passage for supplying the dry gas into the cylinder in the vicinity of the material supply hole. Moreover, it is preferable that the said dry gas supply channel is opening in the said cylinder in the position lower than the said material supply hole. Furthermore, it is preferable that the dry gas supply passage is opened in the cylinder at a position lower than the measuring member. Furthermore, it is preferable that the dry gas supply passage opens into the cylinder at a position shifted in the moving direction of the molding material from the material supply hole.

  The above-described injection device may further include an exhaust unit that exhausts gas from the material supply hole.

  According to the present invention, since the dry gas is blown in the vicinity of the material supply hole of the cylinder, the resin staying in that portion is exposed to the dry gas and dried. Therefore, the resin immediately before being melted in the cylinder can be maintained in a dry state, and adverse effects on the molded product due to the mixing of moisture into the molten resin can be prevented.

  Next, an injection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of an electric injection molding machine provided with an injection apparatus according to an embodiment of the present invention. First, the entire electric injection molding machine will be briefly described. The electric injection molding machine 1 shown in FIG. 1 includes an injection device 10 and a mold clamping device 20.

  The injection device 10 includes a heating cylinder 11, and the heating cylinder 11 is provided with a hopper 12. A screw 13 is provided in the heating cylinder 11 so as to be movable back and forth and rotatable. The rear end of the screw 13 is rotatably supported by the support member 14. A weighing motor 15 such as a servo motor is attached to the support member 14 as a drive unit. The rotation of the metering motor 15 is transmitted to the screw 13 of the driven part via a timing belt attached to the output shaft.

  The injection device 10 has a screw shaft 17 parallel to the screw 13. The rear end of the screw shaft 17 is connected to the output shaft of the injection motor 19 via a timing belt. Therefore, the screw shaft 17 can be rotated by the injection motor 19. The front end of the screw shaft 17 is engaged with a nut fixed to the support member 14. When the injection motor 19 is driven and the screw shaft 17 is rotated via the timing belt, the support member 14 can move forward and backward, and as a result, the screw 13 of the driven part can be moved back and forth.

  The mold clamping device 20 includes a movable platen 22 to which a movable mold 21A is attached, and a fixed platen 24 to which a fixed mold 21B is attached. The movable mold 21A and the fixed mold 21B constitute a mold apparatus 23. The movable platen 22 and the fixed platen 24 are connected by a tie bar 25. The movable platen 22 is slidable along the tie bar 25. Further, the mold clamping device 20 includes a toggle mechanism 27 having one end connected to the movable platen 22 and the other end connected to the toggle support 26. A ball screw shaft 29 is rotatably supported at the center portion of the toggle support 26. A nut 31 formed on a cross head 30 provided in the toggle mechanism 27 is engaged with the ball screw shaft 29. A pulley 32 is provided at the rear end of the ball screw shaft 29, and a timing belt 34 is provided between the output shaft 33 of the mold clamping motor 28 such as a servo motor and the pulley 32.

  In the mold clamping device 20, when the mold clamping motor 28 that is a driving unit is driven, the rotation of the mold clamping motor 28 is transmitted to the ball screw shaft 29 via the timing belt 34. Then, the ball screw shaft 29 and the nut 31 convert the rotational motion into a linear motion, and the toggle mechanism 27 operates. By the operation of the toggle mechanism 27, the movable platen 22 moves along the tie bar 25, and mold closing, mold clamping, and mold opening are performed. A position detector 35 is connected to the rear end of the output shaft 33 of the mold clamping motor 28. The position detector 35 detects the number of rotations or the amount of rotation of the mold clamping motor 28, thereby moving the movable platen connected to the crosshead 30 by the crosshead 30 or the toggle mechanism 27 that moves as the ball screw shaft 29 rotates. 22 position is detected.

  In addition to the above configuration, a dry gas supply device 40 is provided in the injection molding machine according to the present embodiment. The dry gas supply device 40 generates a dry gas, which will be described later, and supplies it to the heating cylinder 11. The resin supplied from the hopper 12 and staying in the heating cylinder 11 is exposed to the dry gas supplied from the dry gas supply device 40 to remove moisture and become dry. Therefore, the resin staying in the heating cylinder 11 is sent forward by the screw 13 while being kept in a dry state, and is melted and injected.

  Next, supply of the dry gas to the heating cylinder 11 will be described with reference to FIGS. FIG. 2 is a sectional view of the heating cylinder 11 and also shows a dry gas supply device 40. FIG. 3 is a sectional view of the heating cylinder 11 taken along line III-III in FIG.

  First, the dry gas supply device 40 will be described with reference to FIG. As described above, the dry air supply device 40 is a device for supplying dry gas to the heating cylinder 11 (more specifically, the heating cylinder 11 via the cooling cylinder portion 11A).

  In the example illustrated in FIG. 2, the dry air supply device 40 includes a gas container 41 that stores dry gas at a predetermined pressure. The dry gas discharged from the gas container 41 is sent to the tank 42 through the check valve and temporarily stored in the tank 42. The tank 42 is provided with a heater 43 for heating the dry gas in the tank 42 to a predetermined temperature. Here, the predetermined temperature is a temperature determined by the molding material (resin) supplied to the heating cylinder 11. More specifically, the temperature is predetermined in order to make the molding material to be used dry. For example, the predetermined temperature is about 80 ° C. to 120 ° C. for a normal resin. The dry gas heated to a predetermined temperature in the tank 42 is supplied to the heating cylinder 11 through the pipe 45.

  The heating cylinder 11 has a material supply hole 11b, and the resin supplied to the hopper 12 is supplied into the heating cylinder 11 through the material supply hole 11b. A screw 13 is disposed inside the heating cylinder 11 so as to be able to rotate and reciprocate. The supplied resin is filled in a space between the inner wall of the heating cylinder 11 and the flight 13 a formed on the screw 13. . The resin as the molding material supplied into the heating cylinder 11 is moved to the front of the heating cylinder 11, that is, leftward in FIG. 2 by the movement of the flight 13 a accompanying the rotation of the screw 13.

  The heating cylinder 11 is provided with a plurality of heaters 11c, and heats the heating cylinder 11 to a predetermined temperature. The resin that moves forward in the heating cylinder 11 by the screw 13 is heated by the heat from the heater 11c. Further, as the resin moves due to the rotation of the screw 13, a shearing force acts on the resin to generate heat, and the resin enters a molten state as it goes to the front of the heating cylinder 11. At the tip of the heating cylinder 11, the resin is completely melted. Here, by moving the screw 13 forward, the molten resin is injected from the nozzle 11a at the tip into the mold.

  In the portion of the heating cylinder 11 where the resin is supplied from the hopper 12, the temperature of the heating cylinder 11 needs to be maintained at a predetermined temperature so that the resin does not melt or soften. For example, the predetermined temperature is about 80 ° C. Since the heating cylinder 11 is heated by the heater 11a, it is necessary to cool the portion where the resin is supplied from the hopper 12 and maintain it at, for example, 80 ° C. or lower. Therefore, a cooling cylinder 11A is provided at the rear end of the heating cylinder 11, and the hopper 12 is attached to the heating cylinder 11 via the cooling cylinder 11A. A passage through which a refrigerant or cooling water flows is formed in the cooling cylinder 11A. By flowing the refrigerant or cooling water therein, the rear end portion of the heating cylinder 11 is cooled and maintained at, for example, 80 ° C. or lower.

  The dry gas supplied from the dry gas supply device 40 is supplied to the inside of the heating cylinder 11 in the portion where the cooling cylinder 11A is provided. Therefore, in the example shown in FIG. 2, the dry gas supply passage 46 is formed through the cooling cylinder 11 </ b> A and the heating cylinder 11. By connecting the pipe 45 to the dry gas supply passage 46, the dry gas heated to a predetermined temperature in the tank 42 is supplied into the heating cylinder 11 through the pipe 45 and the dry gas supply passage 46.

  In the example shown in FIG. 3, the dry gas supply passage 46 is provided in the vicinity of the material supply hole 11b connected to the hopper. More specifically, the dry gas supply passage 46 extends from the lower side of the cooling cylinder 11 </ b> A on the opposite side of the portion where the hopper 12 is attached, and opens to the inner surface of the heating cylinder 11. Therefore, the opening position in the heating cylinder of the dry gas supply passage 46 is a position lower than the material supply hole 11b in the vicinity of the material supply hole 11b. As a result, the dry gas supplied from the dry gas supply passage 46 and heated to a predetermined temperature becomes hot air while removing the gaps between the granular or pellet-like resins supplied into the heating cylinder. And is discharged from the hopper 12 to the surroundings through the material supply hole 11b. Accordingly, the resin staying in the heating cylinder 11, particularly in the cooling cylinder 11A, is exposed to the dry gas, and the moisture in the resin is absorbed by the dry gas, and as a result, the resin is in a dry state.

  Further, the opening position of the dry gas supply passage 46 in the heating cylinder 11 is shifted in the direction in which the resin moves in the heating cylinder 11 to a position before the material supply hole 11b (in the direction of the nozzle 11a of the heating cylinder 11). Position). This is because the drying gas is supplied from a position as close as possible to the position where the resin begins to soften or melt in the heating cylinder 11 to dry the resin.

  The dry gas may be constantly supplied to the heating cylinder 11, or the dry air before being sent into the heating cylinder 11 can be kept in a dry state by newly sending and replacing the dry air. For example, it may be supplied intermittently.

  Here, the dry gas supplied from the dry gas supply device 40 will be described. The dry gas in the present invention may be any kind of gas as long as it can absorb moisture from the resin when flowing around the resin, and the temperature and humidity are not limited. However, since the dry gas is released into the atmosphere where the injection molding machine is installed, it is preferably non-toxic and nonflammable so that there is no risk of explosion or the like. Such gases include inert gases such as nitrogen and helium. When an inert gas is used, there is an effect that oxygen is removed from the periphery of the resin to prevent oxidation. A particularly preferred gas is air, which is a gas having the same composition as the surrounding atmosphere. For example, the moisture contained in the air may be reduced by using the heater 43 shown in FIG. Further, the air is compressed, the dew point is lowered and dehumidified to generate dry air having a dew point lower than that at room temperature, and this dry air is supplied to the heating cylinder 11 via the dry gas supply passage.

  When a gas different from the molding machine atmosphere is used as the drying gas, the upper opening of the hopper 12 is closed and the drying gas is sucked from the hopper 12 in order not to release the drying gas to the molding machine atmosphere. It is also possible to provide means for discharging. That is, an exhaust means for sucking and exhausting dry gas through the material supply hole 11b of the heating cylinder 11 is provided. The sucked dry gas is discharged to a place away from the molding machine atmosphere, for example, outdoors. When the dry gas has toxicity, it can be discharged to the outside after performing a treatment for neutralizing or removing the toxicity.

  The temperature of the dry gas is usually preferably about 80 ° C to 120 ° C, although it depends on the type of resin used. If the temperature is too low, the drying effect is reduced. Further, if it is too high, the resin is softened or melted, or the temperature in the cooling cylinder 11A is increased, so that there is a problem that a larger amount of cooling water has to flow.

  Further, the humidity when dry air is used as the dry gas is effective to absorb the moisture of the resin if it is lower than the humidity of the air in the heating cylinder 11, but as a condition for efficiently absorbing the moisture from the resin. It is preferable to use air dehumidified in an environment with a dew point temperature of −40 ° C. to 0 ° C. However, the air which heated normal room temperature air to 80 to 120 degreeC is also equivalent to the dry air in this invention.

  Next, the dry gas supply passage 46 will be described. When the dry gas supply passage 46 in the heating cylinder 11 extends upward from the lower side of the heating cylinder 11 as in the example illustrated in FIG. 2, granular resin or resin powder is dried gas. There is a risk of falling into the supply passage 46. Therefore, as shown in FIG. 3, it is preferable to form the dry gas supply passage 46 so as to extend obliquely from above. In this case, since the opening of the dry gas supply passage 46 in the heating cylinder 11 faces downward, there is no possibility that resin particles or resin powder fall into the dry gas supply passage 46 due to gravity, and the dry gas supply passage 46 is clogged with resin. Can be prevented.

  In both the example shown in FIG. 2 and the example shown in FIG. 3, the dry gas supply passage 46 opens in the heating cylinder 11 at a position lower than the material supply hole 11 b in the vicinity of the material supply hole 11 b. Further, the opening position of the dry gas supply passage 46 is preferably lower than the screw 13 as the measuring member in the heating cylinder 11. Furthermore, as described above, the opening position of the dry gas supply passage 46 is a position in front of the material supply hole 11b (position shifted in the direction of the nozzle 11a of the heating cylinder 11) in the direction in which the resin moves in the heating cylinder 11. ) Is preferable.

  Further, as shown in FIG. 4, a dry gas supply passage 46 may be provided behind the material supply hole 11b. In this case, a space without molding material is formed behind the material supply hole 11b even during molding, so that it is possible to prevent the molding material (resin) from entering the dry gas supply passage 46 and clogging. . Furthermore, a seal member 47 may be provided between the screw 13 and the heating cylinder 11 behind the dry gas supply passage 46. By providing the seal member 47, the space between the screw 13 and the heating cylinder 11 can be sealed, and the molding material can be efficiently dried even if the dry gas supply passage 46 is provided behind the material supply hole 11b. Can be. Here, even if the screw 13 advances and retreats, the seal member 47 is disposed at a position where it comes into contact with the cylindrical portion of the screw 13.

  In the above-described configuration, the dry gas supply passage 46 provided in the heating cylinder 11 functions as means for supplying the dry gas to the heating cylinder 11. The dry air supply device 40 may be included in the means for supplying the dry gas to the heating cylinder 11, but the dry air supply device 40 is, for example, a dry gas collectively for the injection devices of a plurality of injection molding machines. It is not always necessary to provide a single dry air supply device 40 for one injection molding machine (injection device), and a single dry air supply device 40 can provide a plurality of injection molding machines. The piping can be connected to supply dry air. That is, one dry air supply device 40 can be used in common by a plurality of injection molding machines. Therefore, as the injection device, it is considered that the dry gas supply passage 46 is formed in the heating cylinder 11 and has means for supplying the dry gas to the heating cylinder 11.

  When supplying dry air by connecting piping from a single dry air supply device 40 to a plurality of injection molding machines, a plurality of injection molding machines can be used rather than attaching a dry air supply device to each injection molding machine. Overall, it is possible to reduce the cost associated with the configuration for supplying dry air.

1 is an overall configuration diagram of an electric injection molding machine provided with an injection device according to an embodiment of the present invention. It is sectional drawing of the heating cylinder of the injection device shown in FIG. It is sectional drawing of the heating cylinder along the III-III line in FIG. It is sectional drawing of a heating cylinder at the time of arrange | positioning a dry gas supply path behind a material supply hole.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Injection device 11 Heating cylinder 11A Cooling cylinder 11a Material supply hole 11b Material supply hole 12 Hopper 13 Screw 13a Flight 20 Clamping device 40 Dry air supply device 41 Gas container 42 Tank 43 Heater 44 On-off valve 45 Piping 46 Dry gas supply passage 47 Seal member

Claims (10)

An injection device having a cylinder to which a molding material is supplied, and a measuring member that is driven in the cylinder and measures the molding material,
The cylinder has a material supply hole for supplying the molding material, and has means for supplying a dry gas heated to a predetermined temperature to the vicinity of the material supply hole in the cylinder. Injection device to do. An injection device having a cylinder to which a molding material is supplied, and a measuring member that is driven in the cylinder and measures the molding material,
The cylinder has material supply holes for supplying the molding material, and has means for supplying dry gas generated by compressing and dehumidifying gas to the vicinity of the material supply holes in the cylinder. An injection device characterized by. The injection device according to claim 1 or 2,
2. The injection apparatus according to claim 1, wherein the dry gas is a gas having the same composition as the ambient atmosphere. The injection device according to claim 1 or 2,
The injection apparatus according to claim 1, wherein the dry gas is an inert gas. The injection device according to claim 1 or 2,
2. An injection apparatus according to claim 1, wherein the humidity of the dry gas is lower than the humidity of the atmosphere in the cylinder. The injection device according to claim 1 or 2,
The cylinder has a dry gas supply passage for supplying the dry gas into the cylinder in the vicinity of the material supply hole. The injection device according to claim 6,
2. The injection apparatus according to claim 1, wherein the dry gas supply passage opens into the cylinder at a position lower than the material supply hole. The injection device according to claim 6,
2. The injection apparatus according to claim 1, wherein the dry gas supply passage is opened in the cylinder at a position lower than the measuring member. The injection device according to claim 6,
2. The injection apparatus according to claim 1, wherein the dry gas supply passage is opened in the cylinder at a position shifted from the material supply hole in the moving direction of the molding material. The injection device according to claim 1 or 2,
The injection apparatus further comprising exhaust means for discharging gas from the material supply hole.

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